Mybatis 的问题，我按照原本的格式写一个操作为什么原先的能成功，而我的不管怎样都会失败呢？

这个项目 Dao 是单独一个项目，然后打成 jar 包添加到 maven。在后台项目里从 maven 引入的。 我想在 Dao 里加一个操作，但是就很简单的查询也会失败。 模仿的样例：
AppUserMapper.java

AppUserMapper.xml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="XXX.dao.AppUserMapper"> <resultMap id="BaseResultMap" type="XXX.entity.AppUser"> <!--实体类映射--> </resultMap> <sql id="Base_Column_List"> <!--查询的值--> </sql> <!--省略--> <select id="selectByPrimaryKey" parameterType="java.lang.String" resultMap="BaseResultMap"> select <include refid="Base_Column_List" /> from app_user where id = #{id,jdbcType=VARCHAR} </select> <!--省略--> </mapper> 

自己写的：
GoodsOff.java

package XXX.entity; import java.io.Serializable; public class GoodsOff implements Serializable { private int id; private String goodsId; private float off; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getGoodsId() { return goodsId; } public void setGoodsId(String goodsId) { this.goodsId = goodsId; } public float getOff() { return off; } public void setOff(float off) { this.off = off; } } 

GoodsOffMapper.java

package XXX.dao; import XXX.entity.GoodsOff; public interface GoodsOffMapper { GoodsOff selectByPrimaryKey(String goodsId); } 

GoodsOffMapper.xml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="XXX.dao.GoodsOffMapper"> <resultMap id="BaseResultMap" type="XXX.entity.GoodsOff"> <id column="id" jdbcType="INTEGER" property="id" /> <result column="goods_id" jdbcType="VARCHAR" property="goodsId" /> <result column="off" jdbcType="FLOAT" property="off" /> </resultMap> <select id="selectByPrimaryKey" parameterType="java.lang.String" resultMap="BaseResultMap"> select * from hbmm_goodsoff where goods_id = #{goodsId,jdbcType=VARCHAR} </select> </mapper> 

我数据库里的表：

REATE TABLE `hbmm_goodsoff` ( `id` int(11) NOT NULL AUTO_INCREMENT, `goods_id` varchar(64) CHARACTER SET utf8mb4 DEFAULT NULL, `off` float DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=22 DEFAULT CHARSET=utf8;